1. Field of the Invention
The invention relates to a single-blade reamer having a blade head with a blade plate and at least one grinding fillet.
2. Relevant Prior Art
Single-blade reamers are of a type known per se and serve for the finishing of holes in workpieces. The guiding of the reamer in the workpiece, which is effected with the aid of at least one guide fillet, is of particular importance. A problem in this connection consists in that, because of the friction of the guide surface of the guide fillet against the wall of the hole, various disturbance effects may occur, which then give rise to inaccurate guiding and even premature wear on the guide fillet. It is true that the disturbance effect of friction is reduced if the hole is flushed with a cooling liquid, usually containing lubricating additives. However, because disposal of this cooling liquid is expensive, there is a tendency to reduce as much as possible the portion added. In contrast to the presently usual guide fillets of bright hard metal, a remedy was therefore sought by proposing coatings of mixed ceramic material in German patent document DE 39 24 998 A1, or plastic material in German patent document DE 40 07 175 A1, and finally of diamond in German patent document DE 42 02 751 A1. The basic principle of these partly contradictory coatings is reduction of friction on the one hand through the self-lubricating property of plastic materials, and on the other hand through the extreme hardness of diamonds. In addition, the affinity of the coating for the material of the workpieces should be so reduced that welding-on of the material is avoided.
It has now been found that the effect hoped for, particularly from diamond coating, although it was for example achieved in the case of aluminum materials, was nevertheless absent in the machining of hardened steel alloys. There is however now an increasing tendency in the manufacturing industry not to effect the hardening of steel parts after the reaming, because this leads to changes of shape, but to carry out the precision reaming of the holes after the hardening. This requirement can be met only inadequately with present guide fillet designs, either because the reaming power is low or the addition of a considerable amount of lubricant is necessary, or because rapid wear of the guide fillets must be accepted.